What about Ashera? It's more subtle, but still major (a form of Ishtar/Inanna), once worshipped as the wife of the Hebrew God, but on her own before, It will likely be taken as a feminine form of Asher, which seems to be quite popular of late (and the pronunciation is Asher-uh). I love many of your choices esp. Guinevere, Isolda, Calista, Cassandra, and Hespera has a softness about it. (Indulge my spelling preferences).

From your lists, of course Morgana is still my number one. Aphrodite and Morgana are magical together. My next four from all the lists in order are:

2. Isis -- If I can only have Cleopatra or Isis, I prefer Isis. It's short and powerful and stands up wonderfully to her sister.
3. Tinuviel -- Love this with Dita. It's not too cute, it's gorgeous
4. Melusine -- she has the oceany feel that Aphrodite has, and she's gorgeous
5. Ostara -- Love it with Dita! Powerful and strong and Starla would be adorable

Comments on the others:

Bellicent -- I love her so much more as a middle
Boadicea -- Love it a lot. I think you'd have to have a C as the 3rd though
Bradamante -- She sounds so harsh to meCirce -- I just don't like her with Aphrodite. She's a wonderful middle, but I don't like the similar endings Cleopatra -- I would rather have Isis. She's great, but not as good as Isis.Guinevere -- I've already given you my arguements as to why it's weird with Morgana. If you find Bellicent weird, why not Guinevere?
Gwenllian -- She's great and I ADORE her but I like others better. She needs to stay as a middleIsolde -- I much prefer Isis. Isolde doesn't do anything for me and her story is lovely but she doesn't live up to her sister
Nimue/Niniane -- Meh. She's a great middle, but I don't like her in the front. Niniane is my favorite of the 2Olympia -- I already told you my weirdness here, but I know what you're going forYavanna -- I do think this is too close to Morgana and I like Morgana a lot better. She's fun though, so keep her for a middleZenobia -- She's beautiful and I love her but not as much as others. Aphrodite and Zenobia as a good A-Z thing but the next would have to be B or Y :PAngharad -- Very harsh sounding next to AphroditeArtemisia -- Gorgeous but I don't like it with Aphrodite. It has contrasting sounds I don't like, and I just don't like Artemis and Aphrodite togetherAtalanta -- She's one of my favorite middles for you. I love her with Morgana. MorganaZephyrineAtalanta
Belphoebe -- I adore her as a middle, but she's too similar to Aphrodite for meCallisto -- Meh. She doesn't do anything for meCassandra -- Love it and Aphrodite and Cassandra as cool together, but I like others better. Middle
Coventina -- Makes me think of covet
Daronwy -- I don't like the sound.
Elbereth/Elentari -- Elentari is cool. I love both of these for the middle, but not for the first
Galadriel -- Gorgeous, love the meaning, love the connections, but she's way to LOTR. Middle
Hespera -- While I like her with Aphrodite, not as much as others. She's a great middleInanna -- Love it, would rank but there are others I like better. Keep for middleIsabella -- WAY to normal next to the others and Aphrodite and very popular. I think of Isabella of Spain, but still
Laudine -- It makes me think of cough drops
Nehalennia -- I'm not entirely sure how to say this one. Help with pronunciation and who this is?Pandora -- You know my thoughts here, and I think the feeling is SO different to Aphrodite. I think you should try to keep it in the middle since you love it
Pulzella -- I just don't like the sound very much, but it would be a cool middleRhiannon -- Very nice and mythological, but very bland to me
Silmarien -- I want this to stay as a middle. I just don't like it as a first next to the othersTitania -- I just prefer Tatiana and though I love the literary connections, I just don't like Tit being in there
Trephina -- This is very cool, and I think it might be my number 6
Undomiel -- I just don't like the sounds with Aphrodite
Valkyrie -- I do love the sound, but prefer the names of the Valkyrie personally Veronika -- this seems entirely too normal next to all the others and Aphrodite

I would suggest stuff but it's storming and I need to get off the computer. I'll be back though.

From the ones currently on your list, I really love: Guinevere (although I do understand the issue with having a Guinevere and a Morgana, it is still beautiful), Gwenllian, and Isolde.

From your new choices, I particularly like:

Cassandra - prettyMelusine - Simply stunning! Probably my favorite from your new list, and it stands up well with AphroditeTitania - This one is very magical sounding to me
Valkyrie - This one I am on the fence about, it's very intriguing to me

Bradamante- I love this so much I based the name of the main character in 'What a Prospect!' on it. He's Bradiganti. So thanks! IsoldeCallisto- Callisto is so soft. It feels like a whisper in the same way that Aphrodite does.CassandraPandora

*I like Angharad too obvs But for me, Morgs and Angharad are the same person, lol.